Self-priming centrifugal pump



July 8, 1941. o. JACOBSEN SELF-PRIMING CENTRIFUGAL PUMP 2 Sheets-Sheet 2.File d Feb. 23, 19:59

OYSTEIN JZJcoBsEIv,

atented duty 8,1941

2,248,174 spar-re can'ranucar. PUMP Oystin Jacobsen, Montgomery County,Ohio, as-

signor to The Durlron Company, Inc.,

Dayton,

Ohio, a corporation of New York Application February 23, 1939, SerialNo. 257,979

Claims.

The present invention relates to self-priming centrifugal pumps and moreespecially to pumps designed to operate at considerable velocities andadapted to handle acids or water containing am 5.

It is somewhat different to prime pumps of the centrifugal type and thustheir operation is considerably interfered with in case the head ofwater is accidentally lost or reduced below a predetermined level, aswhen leaks occur in the system. Moreover, the fluid passing through thepump travels at an extremely high velocity and, since the direction ofthe fluid necessarily changes in passing through the pump, zones ofcontraction appear, which reduces the cross sectional area of thepassing fluid which causes a reduction in theoutput and efficiency ofthe pump.

The primary object of the invention is to provide a centrifugal pumpwhich operates at a higher efficiency than the pumps of this type on'the market.

- Another object is to provide a pump of this character in which thedegree of self-priming is considerably enhanced.

Still further objects are to provide a centrifugal pump, in which thepumping action is maintained even when leaks appear anywhere in thesystem; to provide a centrifugal pump having a suction elbow, and inwhich the fluid is withdrawn from the lower part of the elbow as well asfrom the upper part thereof. The present day pumps withdraw the wateronly from the upper part of the elbow.

These objects are attained, in brief, by providing a repeatedcirculation of the priming liquid in a circuit including the separationchamber to withdraw air from the suction elbow, and introducing thisliquid into the impeller at a position where a zone of contraction wouldnormally occur. Thus, this zone is being continually filled with liquidand the cross sectional area of liquid flowing between the vanes. of theimpeller is cor respondingly increased. The object last mentioned aboveis carried out, in brief, by providing an opening in the impeller casingand causing the fluid to pass over the lower portion of the suctionelbow through theopening into the impeller.

The invention will be'better understood when reference is made to thefollowing description and the accompanying drawings in which- Figure 1shows a view in cross section, except for a few minor parts'of theimproved pump.

Figure 2 is an enlarged view,taken along line 2-2 in Figure 1 andlooking in the direction of the arrows.

Figures 3 and 4 are enlarged cross sectional views of the upper part ofthe impeller and immediately adjacent parts, useful in explaining themanner in which certain improvements provided by this invention serve toincrease the efficiency of the pump. Figure 3 shows the effect obtainedwithout the improvement, while Figure 4 illustrates the enhanced resultobtained by the improvement described hereinafter.

Referring to the drawings in detail, numeral i designates a heavy diskor plate of an acid-resisting metal such as silicon iron, to which issecured, in any suitable manner, a number of arcuate vanes 2, as seenmore clearly in' Figure 2.

The plate i is provided at the center with a cored out hub 3 and a noseportion A which form a compartment for receiving the end 5 of thedriving shaft 8. The end 5 of the shaft is threaded into a cap I of anysuitable metal such as bronze, which is machinable and which metal iscast in place. The cored compartment is provided with ribs 8 whichextend radially inwardly and the metal I is cast about these ribs so asto form a positive lock. The improved locking device is described andclaimed in my copending application Ser. No. 257,978, filed February 23,1939, and entitled "Pump runner assembly.

The shaft 6 is contained within a sleeve 9 which abuts the hub portion 3and bears against a shoulder onthe shaft at III. A packing i I isprovided about the sleeve 9 and is contained within a housing l2 formingpart of the back plate I3 of the pump casing. Longitudinal pressure maybeapplied to the packing in anysuitable manner, for example, by means ofa cap member 14 adapted to move longitudinally with respect to thehousing l2. The packing is kept saturated with grease from a pipe i6which leads to an adjustable grease cup (not shown).

Adjacent the free edge of the vanes 2, there is a casting H whichconstitutes the front plate of the pump housing. 'I'lnscasting formspart of a large irregularly shaped casing which provides a number ofcompartments including the suction elbow indicated at IS, an inletpassage indicated at I! and a throat indicated at'20. The suction elbowtakes the shape of a goose neck and has secured thereto at the bottom aremovable cover 2| for cleaning purposes. The inlet passage is is formedof a pair of spaced portions 22, 23, respectively and extends from thecasing ll, first; axially and then in an upward direction, bearingslightly to the right into the compartment formed by the suction elbow.Thejwall 22 is extended upwardly beyond the wall 23 and then curves tothe right so as to form together with the goose neck portion 24 a throat26, at

which position there are provided a pair of lugs 25. These lugs supporta heavy metal screen or filter 26 which projects downwardly and in are-entrant manner into the suction elbow, as can be readily seen inFigure 1. This screen is provided with a number of openings 21 and itspurpose is to separate the solid materials from the fluid entering thethroat of the suction elbow.

Above the throat 20, the casting terminates in a seat for a gasketed andremovable cover 29, the purpose of which will be explained. Beyond thispoint, the casting draws down to a portion of smaller diameter indicatedat 30, to which the inlet pipe 3| can be bolted as at 32 or otherwise 1secured.

As shown more clearly in Figure 2, the front and back portions 2, I 3 ofthe pump casing terminate at their periphery in a volute shaped casing33 which contains a chamber 34 of similar shape. This chambercommunicates with an outlet passageway or opening 35 formed in anextension of the volute casing and indicated at '36. A gasket seat isprovided on the top of the extension 36 to receive an air or separationchamber 31 by means of the bolts 38. This chamber is preferably ofspherical configuration and is provided at the center, by means of lugs33, with the circular partition 40 which serves to cause the fluid totake divided paths through the chamber. A seat 4| is provided at theupper end of the chamber 36 to receive the outgoing pipe which may, besecured by the bolts 42.

It will be noted that the lowermost side of the volute chamber 34communicates with a drain '43 closed by a plug 43.

ume-reducing effect of the zone of contraction so that the spacesbetween the vanes 2 are kept full of water. at the point where the zoneof contraction would normally occur. As seen more clearly in Figure 4,the improved construction takes the form of an additional conduit orpassageway by which fluid which has been pumped into the volute chamber34 and which might normally flow back along the vanes is caused to beintroduced into the passageways between vanes at the zone of contractionand thus to be recirculated through the pump. This backflow of fluid isa well-known eiiect and it occurs more especially at the top portion ofthe impeller and is due to gravitational effects on the fluid. Theseeifects, of course, become less as the speed of the pump becomesgreater, but in general there is always a certain amount of backflowwhich cannot be avoided. The recirculating fluid is introduced to theimpeller preferably at the zone of contraction, although proportionallygood results may be obtained by introducing the fluid as close aspossible to the zone.

For conducting the recirculating fluid to the impeller, I provide aconduit or passageway indiof walls 48, which are integrally joined atthe top to the inner wall of the volute casing 33. The

opening" is preferably of elongate configuration and extends through thecasing II in a diagonal direction, depending on the direction ofrotation of the vanes 2. Thus, as the vanes are rotatedcounterclockwise, asseen in Figure 2, the openwhich collects in thesuction elbow is through I the inlet passage I 3, into the eyelet of the"pump indicated at 4, the fluid being then forced out centrifugally bythe blades 2 into the volute ,chamber 34 and from thence through theoutlet opening 35 into the air chamber 37!.

This-fluid, of course, travels at an extremely high velocity and changesits direction from the axial to the transverse direction in passing fromthe lower end of the inlet passage l9 into the passageways between therevolving blades or vanes 2. In passing around the corner indicated at ain Figure 3, particularly when traveling at such a high velocity, a zoneof contraction shown at b in Figure 3 is formed. As the velocity offluid becomes greater, the length and width of this zone are increasedin-corresponding degree. Moreover, as can be seen from Figure 1, thelower portion of inlet passageway I3 is of considerably greater sizethan the small narrow passageways between the vanes 2 of the impeller.It is well known in hydraulics that, when a fluid passes ing extends tothe left, as indicated by the dotted lines. As stated hereinbefore, theopening 41 may be positioned anywhere along the depth of the casing II,as seen in Figure 4, but its preferred position is immediately oppositethe zone from a pipe of large size to a. smaller pipe, zones ofcontraction indicated at b in Figure 3.

A comparison of Figures 3 and 4 will show that whereas, in the absenceof an opening in the casing IT, a zone of contraction occurs at thecenter of the impeller, by providing the opening,-

fluid is caused torecirculate from the periphery of the impeller throughthe passageway 46 and the opening 41 to fill the zone of contractionwith fluid. This water which is recirculated is usually of no. greateramount than normally flows back tends to move downwardly through thepassageways of those vanes which are in the vertical 'position for themoment, the velocity of flow and the position attained by thisdownwardly moving fluid. being dependent on the speed of the impeller.The greater the impeller speed the less does the fluid flow backwardly.As the fluid moves downwardly through the vane passageways, and assuminga structure similar to that shown in Figure 3, the fluid will be impededby the zone of contraction b, that is to say, this fluid will flowaround the zone I), causing greater restriction of the space throughwhich the upwardly flowing water has to move- Thus this back-flow fluidcurtails the upward flow of usespears-s ful fluid at the zoneofieontractioniand to that extent-reduces the efllcienoy o! the pump..On the other hand, '=byproviding the: opening 41 at the zone ofcontraction, and. by providin a ready path 46 for the back-flow fluid,the lat r is di- 5 rected against the zone ot'contraction 3, fillingthis zone and-rthus taking up: no more space-at the position of thezone-of contraction than 'ii there were no back-flow fluid. *In'other'words, the zoneof contraction: b (Figure -8)--is.made to 10accommodate the back-flow fluid byproviding the opening 41, and thisfluid: no longer impedes the upwardly flowing fluid by adding to thezone of -contraction.-- Thevane passageways, posi-v tioned upwardly-fromthe 'zone of= contraction, are of suflicient area to accommodate theupwardly moving useful stream of water combined with the back-flowwater. which has-been injected into the vane-passageways at the openingor openings El. Y i j Consequently, the capacity and, therefore, theefiiciency of the pump is" enhanced by the amount of back-flow'fiuidwhich can be accommodated at the zone of contractionand which eventuallyreaches the outlet passageway. To give a concrete example,-the zone ofcontraction in a given pump might easily besuch as to represent a 20%impedance to flow. When the zone is completely filled with fluid-,whichwould normally constitute a back-flow, the efiiciency of the pumpi'senhanced approximately by the same amount.

Another importantaspect of the fluid which leaves the volute chamberand'is recirculated through the pump is the enhancement of the primingability of the pump. The average level of the fluid in the suctionchamber is is indicated by the dot-dash line 0. Under these conditions,a centrifugal pump 'of any type will contlnue to draw water and air fromthe cha.nn=-- 4 ber 18 and thus create a suction by which to draw'fluidup through the pipe 3|. However, due to leaks anywhere in the system,more especially in the pipe 3i and perhaps at the packing i i, the levelof the fluid might abruptly drop from the level c, and in fact to suchan extent that the elbow i8 may be entirely devoid of fluid. In such acase, the centrifugal pump of ,an unimproved design would be unable tocreate the necessary suction in the elbow. However, the pump disclosedherein would still continue to provide the necessary suction, becausethe fluid which had already collected in the chamber 31 would not onlytend'to fill up the suction elbow I8, but in addition would cause acirculating flow of fluid through the passageway 46 and the opening 41to the impeller l and this circulating fluidwould be suflicient toinduce a heavy suction atthe elbow l8, which would, in turn, cause asufficient drawing effect on the fluid in pipe 3|, notwithstanding leaksthroughout the system.

Thus, the passageway 48 and opening 41 serve a two-fold purpose, namely,they render the pump self-priming inproviding an additional circulatoryflow of fluid from the volute and air chambers to the center of theimpeller and also in eliminating the flow-impeding eflects of the zonesof contraction found near the center of the impeller. This eliminationbeing brought about by filling these zones or regions with fluiddiverted from the volute chamber or other outlet passageways.

While I have explained the zone of contraction. as being a region wherethere is a scarcity of fluid due to a change in flow and direction, or 7change in-gthesizeot the flow passageways, it winte -understood thatthis terminology is in.-

' tended to include a contraction in the size of the stream due to anycause whatsoever, for example, due to-local eddies or'other turbulenceswhich prevent free flow of the fluid. v

v =In.-accordance with the second aspect of my invention,-.I:.proposetoprovide a construction including the-pump and its suction elbowaccessoryfby which the pump. obtains fluid not only iromthe upper part0! the elbow, but from the lower part thereof. Thus, the elbow is beingcontinually scoured bythe moving fluid and no part of; the latter ispermitted to remain stationary in the elbow. For carrying out thisfeature, I provide in the lower portion of the wall 23 of the inletpassage is a pair of partitions 49 indicated on Figure 2, to which issecured a wall portion 50, shown in Figure 1. The fourth side of thepassageway 5i is constituted by the lower portion of the casing. ii. Themembers 49 and 50 extend downward from the wall 23, leaving only a smallopening between their lower edge and the bottom of the elbow I8. Anopening 52 is provided in the casing 81 at the upper end of thepassageway 5i. As seen more clearly in Figure 2, this opening is.directed prefers ably in a downward direction toward the im-.- pellerand is also flared to a larger size as the impeller is approached. g Itis-apparent that,- as the impeller is rotated and assuming that thelevel of the water is at c,-

' the entrance to the inlet passageway I9 draws fluid from the upperportion of the elbow, whereas the fluid at the lowerportion of the elbowfinds its way to the impeller-through the passageway 5i and the opening52. This last-mentioned portion of the fluid is that which ordinarilywould remain at the bottom of the elbow and little or no movement wouldbe accorded thereto by pumps oi unimproved type. It is also apparentthat, by providing the opening 52 and the passageway El which extends toa position near the bottom of the suction elbow, the pump is capable ofdrawing water, at least for a limited time, even when the level of thewater in the elbow falls below that indicated at c.

When the pump is installed for the first time so that the suction elbowII is empty. as is also the air chamber 31, the pump may be convenientlyprimed by removing the cover 25 and fllling the elbow with fluid to thenecessary height However, it will be understood that, after the pump hasbeen initially primed in this manner, no further priming is necessaryfor the reasons stated hereinbefore.

It will be understood that I desire to comprehend within my inventionsuch modifications as come within the scope of the claims and theinventlon.

Having thus fully described my invention what I claim as new and desireto secure by Letters Patent is: v

1. A self-priming fluid pump of the centrifugal type comprising animpeller, vanes secured thereto, said impeller and vanes being adaptedto rotate within a casing, an inlet passageway communicating-with theinner ends or the passageways between the vanes and extending angularlythereto to leave a relatively sharp edge at the junction between the'inlet and vane passageways whereby a zone of contraction is produced inthe region of thesharp edge, an outlet passageway leading from theperiphery of the impeller through said casing to the exterior of thepump,

and a passageway for priming fluid leading i'rom the periphery of theimpeller through the casing adjacent said sharp edge and leading to saidzone of contraction.

and a passageway tor priming fluid leading from the periphery of theimpeller through said casing to a position closely adjacent the innerends the vanes.

3. A self-priming fluid pump of the centrifugal type comprising animpeller, vanes secured thereto, said impeller and vanes being adaptedto rotate within a casing, an inlet passageway communicating with theinner ends of the passageways between the vanes and extending angularlythereto whereby a relatively sharp edge appears between the inlet andvane passageways,

an outlet passageway leading from the periphery of the impeller throughsaid casing to the exterior of the pump, and a passageway for primingfluid leading from the periphery of the impeller through said casing toa position in one of the vane passageways closely adjacent said sharpedge of the casing.

4. A fluid pump of the centrifugal type having a casing and comprisingan impeller, vanes secured thereto .to form passageways, aninlet-passageway leading to the center of the impeller, a suction elbowforming part of the inlet passageway and having a portion positionedbelow the center of the impeller, a passageway extending partiallyacross said suction elbow to leave an opening between the edge of thepassageway and the lowermost portion of the elbow, and means including adrainage aperture communicating with the space in the region of thecenter of the impeller and said passageway tor draining fluid from thelowermost portion of the elbow.

5. A fluid pump of the centrifugal type having a casing and comprisingan impeller, vanes secured thereto to form passageways, an inletpassageway leading to the center of the impeller, a suction elbowforming part of the inlet passageway and having a wall portion whichextends from the casing wall into the elbow intermediate the upper andlower surfaces thereof, a partition extending downwardly-from said wallportion to a position short of the lowermost surface of the elbowwhereby an opening is left between the edge of the partition and thelower surface of the elbow, said partition extending substantiallyparallel to the direction of the impeller and forming with the casingwall adjacent said vane passage- I ways a compartment which opens intothe suction elbow, and anaperture leading from the space at the centerof the impeller to said compartment, said aperture being positionedabove the lower surface of said elbow. I

OYSTEIN J ACOBSEN

